[media] Documentation: devicetree: Add document bindings for mtk-cir

Device-Tree bindings for Mediatek consumer IR controller

found in Mediatek SoC family

Required properties:

- compatible	    : "mediatek,mt7623-cir"

- clocks	    : list of clock specifiers, corresponding to

		      entries in clock-names property;

- clock-names	    : should contain "clk" entries;

- interrupts	    : should contain IR IRQ number;

- reg		    : should contain IO map address for IR.

Optional properties:

- linux,rc-map-name : see rc.txt file in the same directory.

Example:

cir: cir@10013000 {

	compatible = "mediatek,mt7623-cir";

	reg = <0 0x10013000 0 0x1000>;

	interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_LOW>;

	clocks = <&infracfg CLK_INFRA_IRRX>;

	clock-names = "clk";

	linux,rc-map-name = "rc-rc6-mce";

};